21990211 has 4 divisors (see below), whose sum is σ = 22002624. Its totient is φ = 21977800.

The previous prime is 21990193. The next prime is 21990257. The reversal of 21990211 is 11209912.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21990211 - 2⁵ = 21990179 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21990611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2995 + ... + 7276.

It is an arithmetic number, because the mean of its divisors is an integer number (5500656).

Almost surely, 2^21990211 is an apocalyptic number.

21990211 is a deficient number, since it is larger than the sum of its proper divisors (12413).

21990211 is a wasteful number, since it uses less digits than its factorization.

21990211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12412.

The product of its (nonzero) digits is 324, while the sum is 25.

The square root of 21990211 is about 4689.3721328127. The cubic root of 21990211 is about 280.1623675621.

It can be divided in two parts, 21990 and 211, that added together give a square (22201 = 149²).

The spelling of 21990211 in words is "twenty-one million, nine hundred ninety thousand, two hundred eleven".